Tesco Steel & Engineering manufactures ASTM A350 LF2 long weld neck flanges — the cold side of −29 °C: low temperature carbon steel, UNS K03011, Class 1 supply — with ASME B16.5 flange ends in Classes 150–2500 and the barrel made to order. The construction is the A105 workhorse's: the flange and the nozzle in one forging, one closing weld at the shell. What LF2 adds is the certificate that is its entire identity: Charpy V-notch impacts averaging 20 J at −46 °C on every heat — proof that the steel stays tough where unproven carbon steel may snap — with the tensile deliberately capped at 655 MPa because in cold service, excess strength is the enemy of toughness. LNG and refrigerated terminals, cold-climate plants, and the blowdown systems that auto-refrigerate themselves are its home ground; NACE MR0175 sour duty pairs naturally with the same capped hardness. Standard, heavy-barrel and equal-barrel patterns, lengths 150/230/300 mm from stock, bores to schedule. Facings: RF / FF / RTJ. Every lot with EN 10204 3.1/3.2 MTC carrying the Charpy results. ISO 9001:2015, made in Mumbai, India — exported to 50+ countries.
ASTM A350 LF2 Class 1 · UNS K03011Charpy 20 J avg at −46 °C — The IdentityTensile 485–655 MPa — Capped for ToughnessThe Cold Side of −29 °CB16.5 Flange Ends · Class 150–2500Barrel: Length & Bore to OrderLNG · Refrigerated · Blowdown · SourEN 10204 3.1 / 3.2 · ISO 9001:2015
ASTM A350 LF2 Long Weld Neck Flanges — Specifications at a Glance
What is an ASTM A350 LF2 Long Weld Neck Flange?
The cold-certified nozzle forging. An ASTM A350 LF2 Class 1 flange (UNS K03011) whose neck continues as a long, heavy-walled straight barrel — the nozzle itself — bevelled for one closing butt weld at the shell. The identity is the certificate: Charpy V-notch 20 J average at −46 °C on every heat, normalized supply, and a tensile window of 485–655 MPa whose ceiling protects toughness. It is A105's close cousin, certified where A105 is silent — required by code below −29 °C design temperature. Flange ends per ASME B16.5, Classes 150–2500; barrel length and bore stated by you. EN 10204 3.1 with impact results on every lot.
Also searched as: LF2 LWN flange, LTCS long welding neck flange, low temp carbon steel nozzle flange, A350 LF2 Cl.1 LWN, K03011 flange — all the same product. Related pages: the facings — LWNRF / LWNFF / LWNRTJ — the long weld neck hub, the A105 LWN above −29 °C, the LF2 socketweld on small bore, and the LTCS hub.
ASTM A350 LF2 LWN Flange Specifications
ASTM A350 LF2 Long Weld Neck Flanges are available in the following specifications:
Material Grade
ASTM A350 LF2 Class 1, UNS K03011 — 1.0566 equivalent; Class 2 and LF3 only where specifications name them
Impact Requirement
Charpy V-notch at −46 °C, 20 J average of three (Class 1) — results on every certificate
Heat Treatment
Normalized (standard) — the grain refinement the impact numbers depend on; furnace records retained
Construction
Integral heavy-walled straight barrel, bevelled weld end (37.5° standard) — one closing butt weld at the shell, no pipe nipple
Flange End
OD, drilling, facing and P-T ratings per ASME B16.5 (Group 1.1); EN 1092-1 drilling to order
Size
1/2"NB to 24"NB per B16.5; larger to order per B16.47 or drawing
Class
150#, 300#, 400#, 600#, 900#, 1500#, 2500#
Barrel
Length overall to order — 150 / 230 / 300 mm common stock; bore to pipe schedule ID or special; standard, heavy-barrel (HB) and equal-barrel patterns
Facings
Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) with groove per B16.20
Service Notes
Required below −29 °C design temperature; serves to −46 °C per certificate; NACE MR0175 hardness control pairs naturally; LF3 beyond
Testing
Chemistry, mechanicals & Charpy per heat; hardness checked; barrel bore and length gauged piece by piece
Certification
EN 10204 3.1 with impact results (standard) / 3.2 witnessed; NACE MR0175 where specified
What the Impact Certificate Buys
Proof Where the Codes Refuse to Assume
Carbon steel turns brittle somewhere below zero — the Charpy test proves this heat's transition sits below −46 °C, which is why the −29 °C code boundary hands the duty to LF2.
Strength Capped on Purpose
485–655 MPa — the ceiling is the feature: carbon trimmed, manganese raised, normalizing mandatory — every dial turned toward toughness, then proven by test.
The One-Forging Nozzle, Cold-Rated
The LWN argument survives the temperature drop intact: one certificate (now carrying Charpy values), one closing weld, integral metal where refrigerated vessels want reinforcement.
Cold + Sour in One MTC
Blowdown auto-refrigerates, and sour systems blow down: LF2's capped hardness sits naturally inside NACE MR0175 — one forging answers both specifications at once.
Specification Notes — Getting LF2 Long Weld Necks Right
Three honest notes.Above −29 °C, LF2 is optional:A105 serves at lower cost — LF2's case above the line is fleet standardisation, done knowingly; below the line it is not a choice at all. The weld must be as cold-proof as the forging: impact-rated consumables (E7018-1 class), controlled heat input, and WPS qualification with weld and HAZ impacts on coded work — a tough forging spent by a careless weld certifies nothing. And −46 °C is the certificate's edge: designs colder than that leave Class 1's proof — the nickel-alloyed LF3 grade (tested at −101 °C) continues the family, and our quotation will say so when your data sheet crosses the line.
How Our LF2 LWN Flanges Are Manufactured
1
Forging — each piece individually forged from the certified LF2 heat with the barrel integral — no welded build-ups — in any section up to the heaviest HB patterns.
2
Normalizing — the mandatory grain-refining treatment the impact numbers depend on; furnace records retained against the heat number.
3
Impact testing — Charpy V-notch specimens struck at −46 °C, three per heat-treatment lot, 20 J average required — results printed on the certificate.
4
Machining — flange end to ASME B16.5; barrel turned to pattern (standard / HB / equal) and bored to the ordered schedule or drawing; RF serrations, flat face or RTJ groove per B16.20; weld end bevelled 37.5°.
5
Testing & marking — chemistry and mechanicals per heat; hardness checked (NACE limits where specified); marked with grade, size, class, schedule and heat number.
6
Certification & packing — EN 10204 3.1 MTC with tensile, yield and Charpy values (3.2 witnessed on request); faces and bevels protected, packed sea-worthy.
Where LF2 LWN Flanges Are Used
Everywhere the thermometer crosses the code line: LNG and LPG terminal nozzles, refrigerated ammonia and propane storage, cold separators and knock-out drums in gas processing, blowdown and flare knock-out systems that auto-refrigerate, cold-climate plant designed to arctic minimums, and sour-gas hardware whose depressurisation case drives the material both cold and NACE at once. Production and supply below:
Seven elements — the minimum design temperature is the one that picks the grade:
1
Size & standard — e.g. 6″ NB ASME B16.5.
2
Pressure class & facing — 150#–2500#; RF (the default), FF or RTJ with ring number.
3
Barrel length — overall, face to weld end: 150 / 230 / 300 mm stock or any stated length.
4
Barrel bore & pattern — pipe schedule to match or finished bore in mm; standard, heavy barrel or equal barrel; weld-end prep if non-standard.
5
Grade line & design temperature — ASTM A350 LF2 Class 1 (Class 2 / LF3 only if named); the minimum design temperature stated — it is what selects between A105, LF2 and LF3; NACE MR0175 where applicable.
6
Certification — EN 10204 3.1 with Charpy results (our standard) / 3.2 witnessed.
An ASTM A350 LF2 long weld neck flange is a forged low temperature carbon steel flange — UNS K03011, the impact-tested counterpart of everyday A105 — whose neck continues as a long, heavy-walled straight barrel that is itself the nozzle, bevelled at its far end for one closing butt weld made out at the vessel shell or header. What LF2 adds is the certificate the codes demand below -29°C: every heat is Charpy V-notch tested at -46°C, averaging 20 J minimum in the Class 1 standard supply, with normalized heat treatment and a tensile deliberately capped at 655 MPa to keep the steel tough rather than merely strong. Flange ends follow ASME B16.5 in Classes 150 to 2500; the barrel is machined to the ordered length and bore. LNG, refrigerated-gas and cold-climate nozzles are its home ground.
How does a long weld neck differ from a standard weld neck flange?
Geometry and mission. A standard weld neck's hub tapers quickly down to the pipe's outside diameter and wall, ending in a weld bevel a few centimetres from the flange face — it is built to butt-weld to pipe and continue as a piping run. A long weld neck keeps a full-section straight barrel for its entire length: no taper to pipe dimensions, wall far heavier than the matching schedule, length made to order. The mission follows the shape — the LWN is not a fitting on a pipe run but a nozzle in its own right, projecting through insulation, vessel walls or exchanger channels, with the butt weld relocated to the shell side where the fabricator wants it. In one certified forging it replaces the weld neck flange, the pipe nipple and one whole circumferential weld.
What does the Charpy impact certificate actually certify?
That the steel's brittle transition sits safely below your service temperature. Carbon steel has a ductile-brittle transition: warm, it tears with energy absorption and warning; cold enough, the same steel snaps like glass — the failure mode behind history's famous cold fractures. The transition temperature varies heat by heat with chemistry, grain size and heat treatment, so the codes refuse to assume it: below -29°C design temperature they require proof, and the Charpy V-notch test is that proof — three notched specimens struck at -46°C, required to absorb 20 J on average for LF2 Class 1. The certificate therefore is not paperwork about strength; it is documented evidence that this particular heat, in this heat-treated condition, stays tough at temperatures where unproven steel may not. That is the entire difference between this page and the A105 page — and below -29°C it is everything.
Why does LF2 cap its tensile strength at 655 MPa?
Because in carbon steel, excess strength is the enemy of toughness. The same metallurgy that pushes tensile upward — higher carbon, faster cooling, harder microstructures — pushes the ductile-brittle transition upward too, exactly the wrong direction for cold service. So where A105 states only a minimum, LF2 states a window: 485 MPa minimum to carry the rating, 655 MPa maximum to keep the steel on the tough, forgiving side of its own chemistry. The cap works alongside the ≤0.30% carbon, the manganese allowance raised to 1.35% (manganese buys toughness where carbon buys brittleness), and mandatory normalizing. A useful side effect: the capped strength and hardness sit naturally within NACE MR0175's sour-service limits, which is why LF2 handles cold-plus-sour duty in one certificate.
A105 or LF2 — when is the impact-tested grade required?
The boundary is -29°C (-20°F) minimum design temperature, and the codes draw it, not preference. Above it, A105 serves and is the economical default — the two grades are close chemical cousins and their flanges are otherwise interchangeable in dimensions, ratings and welding. At or below it — LNG and LPG systems, refrigerated storage, cold-climate design temperatures, and the frequently-forgotten case of blowdown and depressurisation, where auto-refrigeration chills hardware far below ambient — the design requires impact-tested material, and LF2 is the industry's standard answer at a modest premium. Mixed plants often standardise nozzles on LF2 outright, buying one certificate that covers both sides of the line. State the minimum design temperature on the enquiry and the grade selects itself.
What is the difference between LF2 Class 1 and Class 2?
The impact test temperature. Class 1 — the standard, stocked, near-universal supply — certifies Charpy energy of 20 J average at -46°C, comfortably guarding the -29°C code boundary with margin. Class 2 certifies a higher energy but at only -18°C, a warmer test that suits a narrow band of applications and is rarely specified in practice; a Class 2 certificate does not satisfy a design calling for proof at -46°C. Unless your specification explicitly says Class 2, LF2 means Class 1 — it is what this page describes, what our certificates document, and what the trade assumes. Where projects need proof at still lower temperatures, the LF3 nickel-alloyed grade (tested at -101°C) continues the family; our LTCS pages cover it.
What is the chemical composition of ASTM A350 LF2?
Carbon ≤0.30%, manganese 0.60-1.35%, silicon 0.15-0.30%, phosphorus ≤0.035% and sulphur ≤0.040%, with residual caps of copper ≤0.40%, nickel ≤0.40%, chromium ≤0.30%, molybdenum ≤0.12% and vanadium ≤0.08%. Read it against A105 and the toughness tuning shows: carbon trimmed from 0.35 to 0.30 (carbon raises the brittle transition), manganese allowed up to 1.35 against A105's 1.05 (manganese lowers it), silicon in a tighter killed-steel window. Nothing here is exotic — it is the same honest carbon steel family, adjusted a few tenths in toughness's favour and then proven by test. Chemistry is verified per heat and travels on the EN 10204 3.1 MTC beside the Charpy results.
What are the mechanical properties of LF2 long weld neck flanges?
Tensile strength 485-655 MPa (70-95 ksi) — a window, with the ceiling explained above — yield strength 250 MPa (36 ksi) minimum, elongation 22% minimum, hardness capped at 197 HB, and the defining line: Charpy V-notch 20 J average at -46°C, Class 1. The flange rating side is identical to A105's: B16.5 material group 1.1 pressure-temperature tables govern, so an LF2 flange gives up nothing in rating while adding the low-temperature certificate — one reason mixed-temperature plants standardise on it. Normalizing is the standard heat treatment, refining the grain that the impact numbers depend on, and every certificate states condition, tensile, yield and the three Charpy values.
How are the barrel length and bore of a LWN specified?
Two numbers that belong on every enquiry. Length: measured overall from the flange face to the weld end — 150 mm (6"), 230 mm (9") and 300 mm (12") are the common stock lengths, and any length machines to order; state it explicitly, because 'long' is not a dimension. Bore: the barrel is drilled and bored to order — most commonly to match the inside diameter of the connecting pipe schedule, sometimes cylindrical special bores for level bridles, instrument standpipes or restriction work; state the schedule or the finished bore in millimetres. Add the weld-end preparation (standard 37.5° bevel unless told otherwise) and the nozzle is fully defined.
What are standard, heavy-barrel and equal-barrel LWN flanges?
Three barrel weights for three duties. The standard LWN carries a barrel a little heavier than the matching pipe — the general-purpose vessel nozzle. The heavy-barrel (HB) pattern thickens the wall substantially — often approaching the hub section for its full length — for high-pressure nozzles, heavy nozzle loads and reinforcement-limited openings, where the extra metal does the area-replacement work the code asks of a vessel opening; refrigerated-gas bullets and cold separators use it constantly. The equal-barrel pattern keeps the barrel outside diameter equal to the hub for a clean cylindrical profile — favoured on manway and instrument connections. All three share B16.5 flange ends; the design calculation or the equipment drawing decides which is wanted.
How is an LF2 long weld neck welded — does the impact rating survive?
It survives if the welding respects it — the joint must be as cold-proof as the forging. Practice is carbon steel welding with three disciplines added: consumables chosen with certified low-temperature Charpy values of their own (E7018-1 is the classic), heat input controlled so the HAZ grain stays fine — toughness is a microstructure property, and careless heat coarsens it — and the same thick-section rules as any LWN: preheat above roughly 25 mm, interpass control, PWHT where the governing code requires it (which itself must be qualified not to degrade the impact properties). Coded low-temperature work qualifies the WPS with impact tests in weld and HAZ, closing the loop. The bevel arrives machined 37.5°; the metallurgy arrives certified; the weld's job is not to spend either.
Does LF2 cover sour service as well as cold?
Yes — and the pairing is common enough to be the grade's second career. NACE MR0175 / ISO 15156 accepts LF2-class forgings under the same carbon steel rules as A105: hardness controlled to 22 HRC (237 HB) maximum with welding procedures that keep weld and HAZ within the limit — and LF2's capped tensile, trimmed carbon and normalized condition sit naturally inside those numbers. Cold sour gas is a real duty: depressurising a sour system auto-refrigerates it, so the material that needs H2S compliance frequently needs the -46°C certificate at the same moment, and LF2 answers both with one MTC. State the NACE requirement with the minimum design temperature on the enquiry; hardness testing and any supplementary sour requirements are documented at order.
What sizes and pressure classes do LF2 LWN flanges come in?
Identical coverage to the A105 page, because the flange end is the same B16.5 hardware: ½" to 24" NB in Classes 150, 300, 400, 600, 900, 1500 and 2500, with the full class-by-class LWN dimension charts on this site, larger diameters forged to order against B16.47 or drawing dimensions, and EN 1092-1 drilling machined on the same barrels. The LF2 order book skews recognisably cold: Class 150/300 refrigerated-tank and exchanger nozzles, Class 600-900 gas-processing vessels, and Class 1500-2500 heavy-barrel patterns on high-pressure cold separators and letdown systems. State size, class, barrel length and bore together — the four numbers define the forging — and our quotation returns price, unit weight and delivery per class.
What details are needed to get an accurate LF2 LWN flange quotation?
Seven elements plus commercial terms: (1) size and dimensional standard — e.g. 6" NB ASME B16.5; (2) pressure class — 150 to 2500; (3) facing — RF (the default), FF or RTJ with ring number; (4) barrel length overall, face to weld end — 150/230/300 mm stock or any stated length; (5) barrel bore — pipe schedule to be matched or finished bore in millimetres, with pattern (standard, heavy barrel, equal barrel) and weld-end prep if non-standard; (6) the grade line — ASTM A350 LF2 Class 1 (Class 2 or LF3 only if your specification names them) — with the minimum design temperature stated, plus NACE MR0175 where applicable; (7) certification — EN 10204 3.1 with Charpy results (our standard) or 3.2 witnessed. Add quantity and destination; quotations normally within 24 hours.
Who manufactures ASTM A350 LF2 long weld neck flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing ASTM A350 LF2 Class 1 long weld neck flanges with B16.5 flange ends from ½" to 24" NB (larger to order) in Classes 150-2500, in standard, heavy-barrel and equal-barrel patterns — each forged individually from certified heats, normalized with furnace records, Charpy tested at -46°C with results on the certificate, machined with the barrel bored to the ordered schedule or drawing, bevelled for the closing weld, hardness checked, and marked with grade, size, class, schedule and heat number. Supplied with EN 10204 3.1/3.2 certification and NACE MR0175 compliance where specified — alongside the A105 LWN workhorse, the LWNRF/LWNFF/LWNRTJ facing pages and the complete LTCS family. Exported to more than 50 countries.
